qhy5l II spacing

[rob0971]

Hi all,

I am thinking of buying this camera for guiding with a ST80. As this is probably a popular combo, I was wondering what distance the cam needs to be from the back of the black part of the focuser to achieve focus. I am planning on using this cam with a bright star flip mirror so will need some kind of eyepiece holder to fit the cam in also. Will I be able to achieve focus with the flip mirror with a eyepiece holder fitted or will I need extra spacing or will it be too far?

Cheers

Rob

[rwg]

Hi Rob,

I have the QHY5LII and the flip mirror, but not an ST80, so I can't answer your question exactly. However, I just tried putting the QHY cam into the rear port of the mirror (I have a simple T thread eyepiece holder in this port). The QHY cam comes with a range of different screw on fronts (at least in the 'pro' kit or whatever it's called). I used the thinnest of these which is about 3mm thick and is an IR block filter. In this configuration, I can push the camera forward until the sensor is roughly at the line of the back of the main box of the flip mirror - any further than that and the front of the camera starts to foul the mirror.

This should be far enough in to reach focus I should have thought - you can always check by locating the focus plane by projecting onto a piece of white card. If you can project a focussed image of a distant object onto a piece of card held behind the back of the flip mirror box (mirror up, nothing in the rear port), then you should have enough focus travel to reach focus on the camera. If the focus plane turns out to be a long way back from the back of the flip mirror then you may need to use T ring extensions etc to push the camera further back, but that's not a problem.

One thing to be aware of is focal reducers - they can cause problems because they tend to a) move the focal plane closer to the back of the telescope and lengthen the stack of gadgets you have screwed on the back of your scope. If you ever add a focal reducer to the mix it might take you from 'yes I can achieve focus' to 'no I can't'.

Robin

[martin_h]

If not using the diagonal you wil need at least a 50mm spacer.

[JamesF]

Whereabouts in Somerset are you, Rob?  If you're out my way you could always nip over and try it out.

If you can get a male T-thread to 1.25" adapter I don't think you should have any major problems reaching focus because of the shape of the camera allows it to slide as far forward as the flip mirror will allow.

James

[A320Flyer]

Hi Rob,

I have this exact combination. The attached pic shows the position of the camera in focus. Hope this helps.

Bill

[rob0971]

Thanks all, that's just what I need!

Robin, great idea with the piece of card, would have never thought of that.

James, thanks for the invite. I am near Bridgwater.

Bill, great photo many thanks. Is that a 12 mm illuminated eyepiece?

Seems to be quite a common guiding set up so thought you lot would come up trumps. Many thanks again.

Rob